22 REPORTS ON THE STATE OF SCIENCE.—1917. 
was found to be a function of the rate of shear, and not, as has been 
tacitly assumed in measurements with the capillary viscometer, inde- 
pendent of it. A similar result for emulsoid sols had been obtained 
by Hatschek in 1913. The theoretical reasons why Einstein’s formula 
fails, and the general difficulties of a universally applicable formula for 
systems of two liquid phases, have been fully discussed by v. Smoluchowski. 
As regards emulsoid sols, Hatschek’s formula has been applied 
to the calculation of the solvation factors of proteins by Miss Chick, 
and of rubber in various solvents by Kirchof. The latter’s results are of 
interest, as a comparison is possible between the amounts thus calculated 
from viscosity measurements and the amounts taken up by the rubber 
in the preliminary swelling—remarkable agreement exists between the 
two sets of values. Arrhenius has criticised the figures for proteins, 
or rather the viscosity formula leading to them, as the hydration factors 
are much in excess of those found for hydrates of salts in solution. By 
applying his logarithmic formula to Miss Chick’s measurements he obtains 
hydration factors of the same order as those of electrolytes. Hatschek 
has, however, shown that the application of Arrhenius’s formula to sols 
in organic solvents (rubber and nitrocellulose) leads to factors which 
sometimes are negative, and thus without any physical meaning, and 
sometimes positive, but many times larger than those to which Arrhenius 
takes exception. Ci. ; 
The great importance of viscosity measurements as the most delicate 
means of tracing slight changes in colloidal solutions is fully recognised, 
but in the present state of theory all that can be deduced from such 
measurements is that some change has taken place, the nature of which 
is either a matter for speculation or for empirical interpretation. As the 
latter is sufficient in many instances, viscometric methods appear to find 
increasing use in fields as widely different as the industries of rubber and 
nitrocellulose on one hand, and physiology and pathology on the other. 
There is also a fairly general and gratifying tendency towards the use of 
correctly designed capillary viscometers, instead of the grossly incorrect 
types used for other industrial purposes. 
Further decided progress must depend on the development of theory, 
which, considering the great inherent difficulties of mathematical treatment 
and the incompleteness of our knowledge of even simple liquids and binary 
mixtures, cannot be expected to be rapid, and also on the much extended 
use of methods of measurements permitting variation of the rate of shear 
within wider limits than have so far been attained. 
BIBLIOGRAPHY. 
Experimental and Technical. 
The Viscostalagmometer: Methods for determining Surface Tension, Viscosity and 
Adsorption. J. Trause. ‘ Biochem. Zeitschr.’ 1912, 42, 500. 
The Viscosity of India Rubber Sols. P. ScurpRrowiTz and A. H. Go~pssprouan. 
‘Le Caoutchouc et la Guttapercha,’ 1912, 9, 6220. 
Studies on the Vulcanisation of India Rubber. Gustav Brrnstery. ‘ Koll. 
Zeitschr.’ 1912, 11, 185. (Viscosity of sols of vulcanised India Rubber.) 
Colloidal Sulphur. Sven Opzn. ‘ Zeitschr. phys. Chem.’ 1912, 80, 709. (Viscosity 
of Sulphur Sols of different degrees of dispersity.) 
The Mae of Casein Sols. Harrimtts Cuick and C.J. Martin. ‘Koll. Zeitschr.’ 
1912, 11, 102. 
The Relation between the Resin content and the Viscosity of India Rubber Sols. 
J. G. Fou. ‘Gummi Zeitg.’ 1912, 7, 247. 
